Thermocouple switch



April 15, 1941. e. F. LAING THERMOCOUPLE SWITCH Filed Jan. 22, 1938 nnentor Gordonilbaing fi/ #M.

(Ittomeg Patente d Apr. 15, 1941 UNI-TED STATES PATENT OFFICE THERMOCOUPLE swrrcn Application January 22, 1938, Serial No. 186,368

Claims.

This invention relates to a thermocouple switch and more particularly to one responsive to the direction of a temperature change.

In many cases, it is desirable to have an instrument which is responsive to the direction of a temperature change. One instance of a need for such an instrument is in the burner control art, wherein it is desirable to check the establishment of combustion and the termination of combustion as quickly as possible. Thus in the oil burner control art, it has been quite customary to use a stack switch comprising a bimetallic element connected to one or more switch members through a slip friction connection. Such devices have certain inherent defects such as the instability of the slip friction connection. Moreover it is often difiicult with such devices to get the necessary sequence without undue complication. Thus, again referring to the oil burner control art, it is often desirable to have a switch movable between two contact making positions, in which the switch in moving in one direction makes a second contact before it disengages the first contact and when moving in the other direction disengages the second contact before it makes the first. In other words the switch is overlapping in one direction only.

An object of the present invention is to provide a thermocouple switch which is responsive to temperature change and which comprises broadly a thermocouple having one junction capable of more rapidly absorbing and giving up heat than another, this thermocouple being connected to a polarized relay.

A further object of this present invention is to provide such a switch in which a plurality of armatures are provided which are operated sequentially.

A further object of this present invention is to provide such an arrangement in which the armatures and consequently the switches actuated thereby, are moved with a snap action between their two positions.

In its broader aspects, 8. further object of the present invention is to provide an apparatus of general utility comprising a thermocouple having one junction capable of more rapidly absorbing and giving off heat than another junction thereof, an electromagnetic coil connected thereto, and a member operated by the coil into either one or two positions depending upon the direction of current flow through the coil.

Other objects of the present invention will be apparent from a consideration of the accompanying specification, claims, and drawing of which Figure 1 is a schematic view of an application of the improved switch of the present invention to an oil burner control system.

Figure 2 is an elevational view of the improved switch, taken partly in section along the line 2-2 of Figure 3, and

In which Figure 3 is an elevational view of the improved switch.

While the switch of the present invention is of general applicability, its utility is perhaps best illustrated in connection with an oil burner control system. Accordingly, the switch has been shown in Figure 1 of the drawing as applied to an oil burner control system. It is to be distinctly understood however that so far as the present application is concerned, the invention is notlimited to this application of the switch. The novel features of the oil burner system which arise by reason of the use of this switch are covered in my copending application, Serial No. 186,367, filed of even date herewith and entitled Burner control system which has matured into Patent No. 2,193,516.

Referring to the drawing, an oil burning furnace is generally designated by the reference numeral it. This furnace is shown as being of the hot water type having pipes H and i2 leading to and from radiators or other similar devices (not shown). Extending from the furnace It is the usual stack pipe l3 which is shown in the drawing for the purpose of better showing the combustion responsive apparatus as broken away over a portion thereof.

Associated with the furnace Hi is an oil burner I5, the nozzle 16 of which projects into the furnace. A motor drives the fan controlling the flow of fuel to the nozzle. Only the terminal plate of the motor is shown, being designated by the reference numeral H. Associated with the oil burner is an ignition means designated by the reference numeral Hi. This ignition means may be of any conventional construction, usually consisting of a step-up transformer and electrodes positioned adjacent the oil burner nozzle.

A room thermostat is designated by the reference numeral 22. This thermostat is employed to control the operation of the burner in accordance with the temperature in a @911 or tact arm 24 and serves to impart a snap action to the movement of contact arm 2%. This snap action both serves to prevent arcing between the contact arm 24 and the contact 25 and also serves to impart a differential to the operation of the thermostat to prevent excessive energize,- tion and deenergization of the oil burner motor resulting from a chattering of the thermostat as it approaches its contacts.

A thermal safety switch 30 is employed to interrupt the burner circuit after a predetermined period of time if combustion has not taken place. This switch maybe of any suitable type, one preferable form being that shown in the Denison Patent No. 1,958,081 issued May 8, 1934. The switch is shown for purposes of illustration in the drawing as comprising a pair of switch arms 30 and 32, the latter of which is pivotally mounted. The switch arm 32 is prevented from moving away from switch arm 3! by means of a bimetallic element 33 which in its cold position extends underthe arm of switch blade 32. Associated with the bimetallic element 33 is an electrical heating element 34. This heating element serves to heat the bimetallic element, warping the upper end thereof to the right. If this heating action occurs suf iciently long, the element 33 will be warped as to move from under the end of switch blade 32 allowing this blade to fall away from blade 3i. This switch thus functions as a cut-out mechanism.

A relay is generally designated by the reference numeral 35. This relay comprises a relay coil 36 with which are associated relay switch blades .37 and 38. Switch blades 3? and 38 are adapted .mally biased out of engagement with their reby any suitable means (not spective contacts shown). I

The improved combustion responsive switch of the present invention is generally indicated by the reference numeral 52. An end view of this switch is included in Figure 1 in addition to the elevational view in order to more clearly show the electrical connections to the switch. The details of this switch are best shown in Figures 2 and 3 and reference should be made to these figures in connection with the further description of this switch. The switch consists generally of a polarized relay, the coil'of which is designated by the reference numeral 45 and which is energized by a thermopile 5. The thermopile 45 consists of elements 55, ll, 88, and 49, which elements form pairs of elements having the proper dissimilar thermoelectric characteristics. Thus elements 46 and 48 may consist of iron and elements 4'! and d9 of Constantan. C'onstantan is an alloy consisting of approximately 50 per cent nickel and 50 per cent copper. The junctions between elements 46 and and elements id and t9 are relatively small so as to have very little thermal capacity. The junctions between elements ti and 58, however, and the junctions between elements #16 and 49,, and conductors b and 5!] are relatively large so as to have a considerable heat capacity. The first named junctions are indicated by reference numerals 53 and 5d and the last named by the reference numerals 55, 56, and 5?. All of these junctions are located within the stack. The conductors 5t and bi serve to connect the series connected thermocouples to the coil 3 of the relay. While two thermocouples have been employed in the thermopile, it is to be bers 12.

understood tha any number of thermocouples may be used. In some cases, it is possible to accomplish the results with a single thermocouple. 4

The coil 44 of the relay is located on a bobbin 65 of suitable insulating material, which bobbin is secured to U-shaped pole pieces 66 and 67.

These pole pieces 66 and 61 are secured to the opposite legs of a U-shaped Permanent magnet 68 by means of screws 69 and Ill. The magnet 68 is, in turn, supported upon an insulatin base H by means of a plurality of bracket mem- As best indicated in Figure 3, the relay is provided with three armatures ll, 15, and 15. These armatures 14, I5, and I6 constitute contact arms and are movable between contacts I8 and i3, and 8|, and 82 and 83, respectively. Only'the armature 16 and its associated contacts 82 and 83 are shown in Figure 2. The

arrangement of the contact structures will be described only in connection with this armature. Referring to Figure 2, terminal posts 85 and 86 are secured to the pole pieces 66 and El, respectively. In each case, these terminal posts are secured to the pole pieces "by a screw 81 which extends through an insulating bushing 88. Insulating washers 89 and 90 are interposed between the head of screw 81 and the pole piece and the terminal post and the pole piece. The terminal posts 85 and 86 are slotted adjacent their outer ends and threaded into the slotted portions are screws 82 and 93. The contacts 82 and 83 are carried by-the inner ends of these screws. Referring again in Figure 3, the various armatures H, 15, and 16 are pivotally supported at their mid portion by a pivot pin 9i. Collars 94 and insulating washers 95 surround the pin 9| to keep the armature in properly spaced and insulated relationship.

It will be noted from Figure 2 that the armatures will normally be in either one extreme position or the other due to the fact that when in such an extreme position they are adjacent ends of the pole pieces 66 and 61 which are of opposite polarity. Since there is considerable magnetic attraction holding the armature in its extreme position and the armature is only moved when suflicient force is built up to overcome this attraction, this force will be sufficient to move the armature over center with a snap action whereupon the armature will continue to move by reason of the attracted force exerted bythe opposite ends of the two pole pieces.

The relay, as previously noted, is a polarized relay requiring a reversal of current through the winding 44. This reversal of current takes place by reason of the difierence in size of the junctions 53 and 5d and junctions 55, 56, and 51 on the other. When the temperature within the stack is rising, as occurs upon the initial of combustion, the junctions 53 and 54 will heat up more rapidly than junctions 55, 56, and 51. The resultis that junctions 53 and 54 become the hot junctions and the other junctions the cold ones. Electromotive force is thus generated in one direction, which electromotive force causes a current to flow through winding M in one direction. The apparatus is of such design thatthe current flowing through. coil G l under these conditions causes the armatures ld, i5, and it to rotate in a counter-clockwise direction as viewed from Figure 2. Upon a termination of combustion, the temperature drops and the heat acquired in the meantime by junctions 55, 5t, and 5i will be dissipated less rapidly than that of junctions 53 and 54. The result is that junctions 85, ii, and I! under these conditions become the hot junctions of the thermocouple causing a current flow in the reverse direction. When the current flows in this direction, the armatures 14, II, 'an'il I. are rotated in a clockwise direction to assume the position shown in Figure 3.

It will be apparent from a reference to Figure 3 that the spacing of the various contacts is not uniform. In the illustrative embodiment shown in the drawing, contacts II and ii are least widely spaced from each other and contacts 18 and 19 most widely spaced from each other. The spacing of contacts I3 and 83 is intermediate to that of the other two sets of contacts. Inasmuch as the spacing of the contacts limits the moving of the armature and hence limits the amount the armature, travels past the point at which it is spaced equally from all four ends of the pole pieces, the, spacing of these contacts determines the current required to move the armature from one contact to another. As will be obvious, the less widely the contacts are spaced the less current will be required to eifect a movement of the armature from one contact to am other. Thus upon a rise in the current through coil 44 in either direction, armature 15 will be the first to move, armature 18 the next to move, and armature 14 the last to move.

Operation The various elements of the system are shown in the drawing in the position which they assume when the temperature in the room or other space being controlled is at or above the desired value. Let it be assumed now that the temperature begins to drop. This drop in temperature will eventually cause engagement of contact arm 24 of thermostat 22 with contact 2! whereupon the following circuit will be established to relay coil 36: from line wire 81, which constitutes one of two line wires 91 and ll leading to a suitable source of power (not shown), through conductor 99, bimetallic element 23, contact arm 24, contact 25, conductor I, switch blades 3| and 32, conductor I01, armature 14, contact II, conductor I02, heating element 34, conductors I93 and I", relay coil 38, and conductor I to the other line wire 98. Energization of relay coil 33 results in contact arms 31 and 33 being moved into engagement with contacts 39 and 4|.

The moving of switch blade 33 into engage ment with contact 44 results in the following Oil" cult being established: from line wire 31 through conductor I08, contact 49, switch blade 33, conductors I09 and Ill, oil burner motor l1, and conductors Ill and lli'to the other line wire 38. At the same time, the following circuit is established to the ignition means II: from line wire 91 through conductor Ill, contact, 49, switch blade 38, conductors I09 and H2, armature 16, contact 82, conductor H3, ignition means l3, and conductors H4, Hi, and Ill to the other line wire 93.

The establishment of the previously traced cir cults to the ignition means and to the oil burner motor results in the establishment of the conditions necessary for combustion. At the same .time, the heating element 34 of the thermal "rapidly. As previously explained, junctions 55,

I6, and 51 are not capable of heating as rapidly as junctions 53 and 54. The result is that a current flow takes place through'coil 44 in one direction, which current flow, as previously explained, causes armatures l5, l6, and 14 to move out of engagement with their left-hand contacts and into engagement with their right-hand contacts, in the order named. The moving of armature 15 into engagement with contact 81 results in the following holding circuit being established to relay coil 36: from line wire 91 through conductor 39,-. bimetallic element 23, contact blade 24, contact 25, conductor I00, switch blades 3| and 32, conductor HH, armature 15, contact 8|, conductor ll, switch blade 31, contact 39, conductor 'ili, relay coil 35, and conductor I05 to the other line wire 93. It will be noted that the new holdlng circuit for relay coil 36 is independent of the heating element 34 and constitutes a shunt therearound. Thus as soon as armature 15 engages contact ll, the heating of element 34 is effectively terminated, so that there is an assurance that the oil burner will continue in operation. Shortly after armature 15 engages contact ll, armature ii is moved out of engagement with contact 82 and into engagement with contact member 83. The moving of armature 16 out of engagement with contact 82 interrupts the ignition circuit previously traced. This results in the deenerglzation of the ignition means, the energization of which is no longer needed in view of the establishment of combustion.

Shortly after the ignition has been deenergized, the armature '14 moves out of engagement with contact 18, entirely interrupting the circuit through heating element 34. It will be noted that the transfer from the energizing circuit of relay coil 36 to the holding circuit thereof was accomplished without even a momentary deenergization of relay coil 38.

Under normal conditions, the burner will continue in operation until such time as the thermostat is satisfied, at which time contact arm 24 separates from contact 25 to deenergize relay 35 and terminate the operation of the system. The resulting cooling of the stack temperature will cause the armatures "I4, 15, and 16 to move back into engagement with contacts 78, 80, and

The operation which has just been described is that which occurs when combustion takes place in a normal manner. If combustion does not take place within the time required for heating of the thermal safety switch 34 to the point where bimetallic element 33 moves out from under the blade 32, the separation of switch blades 32 and 3i will take place. The entire system will then be deenergized and cannot be restarted until the safety switch 30 has been reclosed manually.

If combustion does take place but for some reason or other it is interrupted while the thermostat is still calling for heat, the stack will rapidly cool down. The cooling down of the stack causes the junctions 55, 55, and 5'! to become the hot junctions since the heat accumulated therein is less rapidly dissipated than that from junctions 53 and 54. Thus, a current will be generated in relay coil 44 in the opposite direction which, in turn, will cause armatures 15. i6, and 14 to move successively out of engagement with their right-hand contacts and into engagement with their left-hand contacts. The moving of armature 15 out of engagement with contact 8| results in the deenergization of the relay coil 36. Due to the fact that the energizing circuit has been interrupted by the movement of armature M away from contact 18, the interruption of the holding circuit results in the complete deenergization of relay 36. This, in turn, results in the oil burner being deenergized so that atomized fuel is no longer introduced into the furnace. As thetemperature continues to drop the electromotive forcegenerated by the thermocouple will increase with the result that after an interval of time armature '16 will be moved into engagement with contact 82. When such movement takes place, the ignition will'be re-established. Sufficient time, however, elapses between the moving of armature '55 "out of engagement with contact 8i and the, moving of armature 16 into engagement with contact 82 for the fuel accumulated within the furnace to pass up the stack i3. If it were not for this elapse of time, there would be danger of the reestablishment of the ignition causing the :fuel mixture to be ignited with explosive violence. Shortly after armature lit reengages contact 82, armature l4 reengages contact it, reestablishing the originally traced energizing circuit to relay coil 36 through the heating element 34, and thus reenergizing the oil burner motor ill. The conditions necessary for combustion are now established. If the condition causing the termination of combustion is merely a temporary one so that combustion may be reestablished, the operation which takes place will be the same as that previously described. If, however, combustion cannot be established the thermal safety switch 30 will be opened in the usual manner.

It will be .noted that the holding circuit to the relay coil through armature T and contact 8| is dependent upon the closure of relay switch blade 31 with contact 39. This insures that after the thermostat has been satisfied, causing the deenergization of the relay 35, the burner can not be started up again immediately while armature 15 still engages contact 8i. The result is that sufficient time must elapse for the potential of the thermocouple tobuild up in the opposite direction sufficiently to cause armature H to again engage contact 18. This both insures that a check 'will be made as to whether combustion takes place and that time will be allowed for any accumulated gases to pass up the stack.

switching mechanism necessary. In general the device is of particular utility wherever it is desired to operate apparatus in accordance with the direction of a temperature change.

While a specific embodiment of the invention has been shown, it is to be understood that this is for the purposes of illustration only and that the invention is limited only by the scope of the appended claims.

I claim as my invention:

1. A. switching device comprising an electromagnetic coil, a pair of armatures, a switch blade associated with each of said armatures and positioned'thereby, and a switch contact and stop associated with each blade ori opposite sides thereof to limit its movement, the switch contacts and stops for the two blades being reversely disposed so that upon the blades both moving in the same direction one blade moves out of engagementwith its contact and the other moves into engagement with its contact, said contacts and stops being difierently spaced so one blade moves before the other regardless of the direction of current flow.

2. A polarized relay comprising a base, a horseshoe magnet secured to said base, a U-shaped member secured to each pole of said magnet so that the four legs of the two U-shaped members form four poles consisting of two pairs of diagonally disposed unlike poles, a coil secured to said base, a plurality of armatures extending through said coil and pivotally mounted to said base adjacent their mid-points, each of said armatures being movable within said coil between extreme positions in which opposite ends thereof are adjacent the unlike diagonally disposed poles of one pair of poles, means for determining said extreme positions, said means causing the spacings between extreme positions of different ones of said armatures to be different whereby a sequential operation of said armatures results, and a switch member associated with each armature and actuated thereby.

3. A polarized relay comprising an electromagnetic coil, a permanent magnet for producing a substantially constant magnetic field, said magnet having four poles comprising two pairs of diagonally disposed unlike poles, a plurality of armatures pivotally mounted within the magnetic field of said coil, each movable within the field of said magnet between extreme positions in which opposite ends thereof are adjacent the unlike diagonally disposed poles of one pair of poles, a switch blade asociated with each armature and positioned thereby, and switch contacts and stops associated with said switch blades and limiting the movement thereof, said contacts and stops being differently spaced so that said blades are moved in a predetermined sequence regardless of the direction of current flow through said coil.

4. A polarized relay comprising an electromagnetic coil, a permanent magnet for producing a substantially constant magnetic field, said magnet having four poles comprising two pairs of diagonally disposed unlike poles, a plurality of armatures pivotally mounted within the magnetic field of said coil, each movable within the field of said magnet between extreme positions in which opposite ends thereof are adjacent the unlike diagonally disposed poles of one pair of poles, a switch blade associated with each armature and positioned thereby, and a switch contact and stop associated with each blade on opposite sides thereof to limit its movement, the switch contacts and stops for two of the blades being reversely-disposed so that upon the blades both moving in the same direction one blade moves out of engagement with its contact and the other moves into engagement with its contact, said contacts and stops being differently spaced so that one blade moves before the other regardless of the direction of current flow through said coil.

5. A polarized relay comprising an electromagnetic coiL-a permanent magnet for producing a substantially constant magnetic field, said magnet having four poles comprising two pairs of diagonally disposed unlike poles, a plurality of armatures pivotally mounted within the magnetic field of said coil, each movable within the field of said magnet between extreme positions in which opposite ends thereof are adjacent the unlike diagonally disposed poles of one pair of poles, a switch blade associated with each armature and positioned thereby, and a switch contact associated with each blade and adapted to be armature for limiting the movement thereof, the

stop means for each armature being diflerently spaced to permit a difl'erent amount of movement of each armature so that one blade moves before the other regardless of the direction 01' current flow through said coil.

GORDON F. LAING. 

